1. Field of the Invention
In general, the present invention pertains to the field of wireless telecommunications. In particular, the present invention pertains to wireless telecommunication system handover controls.
2. Discussion of the Related Art
Telecommunications systems using wireless telecommunication between mobile and/or stationary transmitting/receiving appliances are specific message systems with a message transmission path between a message source and a message sink. In these systems, base stations and mobile parts are used as transmitting and receiving appliances for processing and transmitting messages in which the message processing and message transmission can be carried out in a preferred transmission direction (simplex operation) or in both transmission directions (duplex operation), the message processing is preferably digital and messages are transmitted via a long-distance transmission path without using wires.
The message processing and transmission is based on various message transmission methods to allow for multiple use of message transmission pats, such as FDMA (Frequency Division Multiple Access), TDMA (Time Division Multiple Access) or CDMA (Code Division Multiple Access). For instance, in accordance with standards such as DECT Digital Enhanced Cordless Telecommunication, as discussed in Nachrichtentechnik Elektronik [Information Technology, Electronics] 42 (1992) January/February, No. 1, Berlin, Germany, or in U. Pilger “Struktur des DECT-Standards” [Structure of the DECT Standard], pages 23 to 29 in conjunction with ETSI Publication ETS 3001750-1 Oct. 9, 1992 and the DECT Publication from the DECT Forum, February 1997, pages 1 to 16], GSM [Groupe Special Mobile or Global System for Mobile Communication. See also, Informatik Spektrum [Information Technology Spectrum] 14 (1991) June, No. 3, Berlin, Del.; A. Mann: “Der GSM-Standard—Grundlage für digitale europäische Mobilfunknetze”, [The GSM Standard—Basis for Digital European Mobile Radio Networks, pages 137 to 152 in conjunction with the publication Telekom Praxis, April 1993, P. Smolka “GSM-Funkschnittstelie-Element und Funktionen”, [GSM radio interface—Elements and functions], pages 17 to 24, UMTS [Universal Mobile Telecommunication System. Further discussion is provided by Nachrichtentechnik Eiektronik, [Information Technology Electronics], Berlin 45, 1995, Issue 1, pages 10 to 14 and Issue 2, pages 24 to 27, and by P. Jung, B. Steiner: “Konzept eines CDMA-Mobiifunk-systems mit gemeinsamer Detektion Für Die Dritte Mobiifunk-generation” [Concept of a CDMA Mobile Radio System with Joint Detection for Third Generation Mobile Radio], and by Nachrichtentechnik Eiektronik, [Information Technology, Electronics], Berlin 41, 1991, Issue 6, pages 223 to 227 and page 234; P. W. Baier, P. Jung, A. Klein: “CDMA-ein günstiges Vieifachzugriffsverfahren für frequenzselek tive und zeitvariante Mobilfunkkanäle”; [CDMA-A Useful Multiple Access Method For Frequency-Selective and Time-Variant Mobile Radio Channels]. Further discussion is given in IEICE Transactions on Fundamentals of Electronics, Communications and Computer Sciences, Vol. E79-A, No. 12, December 1996, pages 1930 to 1937, and P. W. Baier, P. Jung: “CDMA Myths and Realities Revisited”, and IEEE Personal Communications, February 1995, pages 38 to 47. Aslo see, A. Urie, M. Streeton, C. Mourot: “An Advanced TDMA Mobile Access System for UMTS”, Telekom Praxis, 5/1995, pages 9 to 14; P. W. Baier: “Spread-Spectrum Technik und CDMA-eine ursprünglich militärische Technik erobert den zivilen Bereich” [Spread Spectrum Technology and CDMA-An Originally Military Technology Wins Over the Civil Area], and in IEEE Personal Communications, February 1995, pages 48 to 53, in P. G. Andermo, L. M. Ewe rbring: “An CDMA-Based Radio Access Design for UMTS”, in ITO Fachberichte [Specialist Report] 124 (1993), Berlin, Offenbach: VDE Verlag ISBN 3-8007-1965-7, pages 67 to 75, and in Dr. T. Zimmermann, Siemens AG: “Anwendung von CDMA in der Mobilkommunikation” [Use of CDMA in Mobile Communication]. Also see, Telecom Report 16, (1993), Issue 1, pages 38 to 41, a paper by Dr T. Ketseoglou, Siemens AG and Dr. T. Zimmermann, Siemens AG: “Effizienter Teilnehmerzugriff für die 3rd Generation der Mobilkommunikation-Vielfachzugriffsverfahren CDMA macht Luftschnittstelle flexibler”; [Efficient Subscriber Access for 3rd Generation Mobile Communication—The CDMA Multiple Access Method Makes the Air Interface More Flexible], and Funkschau 6/98: R. Sietmann “Ringen um die UMTSSchnittstelle” [Ringing Round the UMTS Interface], pages 76 to 81] WACS or PACS, IS-54, IS-95, PHS, PDC etc., as well as IEEE Communications Magazine, January 1995, pages 50 to 57, and D. D. Falconer et al: “Time Division Multiple Access Methods for Wireless Personal Communications.”
The word message is a generic term which covers not only the information content but also the physical representation of its signal. Despite a message having the same information content, different signal forms may occur. Thus, a message relating to one item can be transmitted in the form of an image, as spoken word, as written word, or as an encrypted word or image.
Transmission types are normally characterized as continuous (analog) signals, while discontinuous signals, although pulses, digital signals may also be used.
In telecommunications systems of the type mentioned above, the handover of an ongoing call or connection is a highly time-critical process, since the continuity of ongoing connections must be ensured. In particular, a distinction is often required between an intracell handover, an intercell handover and an external handover.
In order to carry out a handover between a mobile transmitting/receiving appliance, such as a mobile station or a mobile part connected to a stationary transmitting/receiving appliance, and a base station or a fixed part in a cell, cell-specific information about the adjacent cell, or about a number of adjacent cells is required. The method used to receive this information is referred to as monitoring, wherein the mobile station monitors a control channel, the so-called Broadcast Control CHannel (BCCH) on which the cell-specific information is broadcast by the base station.
One problem with this method relates to how the mobile station obtains the required cell-specific information and the current parameters, such as, frequency, timeslot, and the code of the adjacent base station to which the connection is intended to be transferred by the handover procedure and to which the handover is then intended to be made, when the mobile station is in an uncoordinated, unlicensed scenario. Such a scenerio involves an arrangement where there are a large number of unsynchronized residential base stations, or in a purely coordinated, licensed cellular scenario, say in the case of a TDD-UMTS system, the scenario involves virtually all the physical channels occupied by data traffic which makes it almost impossible to receive the Broadcast Control CHannel of the adjacent base stations due to high data rates encountered.